1. Field of the Invention
The present invention relates to a location based service system and a position information updating method thereof, and more particularly, to a location based service system and a position information updating method thereof in which the number of times a message is transmitted to a position information server and the number of times a database in the position information server is updated are minimized.
2. Discussion of the Related Art
FIG. 1 is an exemplary view illustrating a basic configuration of a related art location based service system. Referring to FIG. 1, the related art location based service system includes a mobile communication terminal 10, receiving position information provided from a plurality of satellites 20, and a position information server 40 receiving position message transmitted from the mobile communication terminal 10 in a wireless mode through a base station 30.
With the development of mobile communication terminals provided with a global positioning system (GPS), various types of location based services (LBS) are being developed. A position information server is required for location based services. The position information server acquires and manages user (i.e., mobile communication terminal) location.
Each moving object basically derives its position (i.e., location) and transmits the position result to the position information server through a wireless communication network to continuously update a position value in the server, so that the position information server maintains a position value having a desired accuracy level. Since the server always maintains the user's current position, the user can promptly be informed of traffic jam, accident, and emergency situations. Additionally, the user's position can quickly be acquired.
To allow the position information server to acquire the user's position, the related art provides a method for periodically (i.e., specified time intervals) requesting the user's position, and a method for acquiring the user's position following a request depending on the types of services.
FIG. 2 is a flow chart illustrating a related art position information updating method. Referring to FIG. 2, a current position value is calculated at a predetermined time tdef in step S21. The mobile communication terminal 10 then transmits the calculated position value to the position information server 40 in step S22. Then, in accordance with decision step S23, a determination is made as to whether time t is equal to the predetermined time tdef. If time t is not equal to tdef, in accordance with the “NO” path out of decision step 23, the method proceeds by looping back and continually checkup whether time t is equal to tdef. If, however, time t is equal to tdef, in accordance with the “YES” path out of decision step S23, the mobile communication terminal 10 calculates its current position based on global positioning system data per step S21.
FIG. 3 is a block diagram illustrating the data format of a position message transmitted by the mobile communication terminal 10 to the position information server in accordance with the related art. Referring to FIG. 3, the message includes a mobile communication terminal identifier msid 11, the position acquisition time_stamp 12, and the position coordinate value coord(x,y,z) 13.
FIG. 4 is a flow chart illustrating another related art position information updating method. This method is identical with the periodically updating method in that the mobile communication terminal 10 derives its position at a constant time interval ‘t’. However, in the method of FIG. 4, the mobile communication terminal 10 does not always transmit the derived position value to the server. Instead, the mobile communication terminal calculates the difference between the current position and the position registered in the server (i.e., the previous position transmitted to the server). If the difference is within (e.g., less than) a threshold value, the derived position value is not transmitted to the server. If the difference is beyond (e.g., greater than) the threshold value, the position value is transmitted to the server to update the position value stored therein. The message is transmitted to the server in the same manner as the periodically updating method.
Accordingly, and as shown in FIG. 4, the mobile communication terminal 10 derives the current position value and stores the value in a memory therein. Then, the mobile communication terminal 10 registers this position value in the server in step S41. After the lapse of a certain period of time, the mobile communication terminal 10 derives the current position value again in step S42, and compares the derived value with the value previously stored in the memory. If the difference between the derived value and the previous value exceeds an allowable threshold value (i.e., error range) as shown by the “YES” path out of step S43, the mobile communication terminal 10 transmits a position message containing the current position to the position information server to update the position value stored in the server, as shown by step S44. At this time, the position message transmitted to the server is also stored in the memory inside the mobile communication terminal 10.
Frequent message transmission and frequent updating of the database in the server are required so that the position information server can maintain a high degree of position accuracy. If the position value is periodically updated, the server should be updated at a period of a certain time ‘t’ as much as the number of moving objects for position collection. A threshold value based position is updated only if the current position is varied at a threshold value or greater than the previous position. Therefore, in case of a vehicle having high mobility per time, frequent update of the server is required. In this regard, it would be highly beneficial to have a method that reduces the number of times message transmission is required, and the number of times the database at the server must be updated.